Update changelog

Author: lfdebrux

CHANGELOG.md

@@ -5,6 +5,7 @@
 ### Fixes
 
 - [#197: Assets: Support Github pages / http_prefix](https://github.com/alphagov/tech-docs-gem/pull/197)
+- [#292: Add code to automatically prefix govuk-frontend assets path with http prefix](https://github.com/alphagov/tech-docs-gem/pull/292)
 
 Thanks [@odlp](https://github.com/odlp) for contributing to this issue and its solution!